End connection for packing strap

ABSTRACT

A strapping connection for a pair of longitudinally extending and transversely overlapping strap ends has a pair of longitudinally extending and interengaging hook formations formed as transversely pushed-out regions of the strap ends and permitting limited movement of the strap ends in one longitudinal direction. In addition the ends are formed in the pair of hook formations with transversely interengaging lock formations fitting transversely snugly together and prohibiting relative longitudinal movement of the strap ends.

FIELD OF THE INVENTION

[0001] The present invention relates to an end connection for packingstrap. More particularly this invention concerns a system for connectingthe ends of metal packing strap.

BACKGROUND OF THE INVENTION

[0002] In order to make secure a package such as a bale it is known toloop a length of steel strip tightly around the package with the endsoverlapping and to connect the ends together. This connection can besimple clip or seal that is applied by a special-duty strapping machine.

[0003] Another system known from German patent document 3,546,021eliminates the use of a separate connector part and forms the two endswith complementary hook formations that fit into each other and preventthe ends from pulling longitudinally apart. The formations are made by atool having an interfitting die/punch assembly that presses againstopposite sides of the overlapping strap ends and creates the hookformations.

[0004] While such an arrangement is extremely simple and effective, ithas the considerable disadvantage that the formations can uncouple whenthe strap is not under tension. Thus if the package is dropped in such amanner as to momentarily compress it near the ends and in effect pushthe strap ends toward each other, the hook formations can disengage fromeach other and thereby disconnect the strap ends.

OBJECTS OF THE INVENTION

[0005] It is therefore an object of the present invention to provide animproved end connection for a packing strap.

[0006] Another object is the provision of such an improved endconnection for a packing strap which overcomes the above-givendisadvantages, that is which is able to hold solidly even when not undertension.

[0007] A further object is to provide and improved system, that ismethod and tool, for forming the connection according to the invention.

SUMMARY OF THE INVENTION

[0008] A strapping connection for a pair of longitudinally extending andtransversely overlapping strap ends has according to the invention apair of longitudinally extending and interengaging hook formationsformed as transversely pushed-out regions of the strap ends andpermitting limited movement of the strap ends in one longitudinaldirection. In addition the ends are formed in the pair of hookformations with transversely interengaging lock formations fittingtransversely snugly together and prohibiting relative longitudinalmovement of the strap ends.

[0009] In the connection according to the invention the hook formationsof each strap end are identical and point in the same direction. Theyfit together to prevent longitudinal separation of the two strap ends,being very strong with respect to tension in the strap. The lockformation prevents the strap ends from separating if the tension isrelieved an relative longitudinal shifting in a direction opposite totheir hook direction is inhibited by the lock formations.

[0010] According to the invention the strap ends are formed with twopairs of longitudinally extending and interengaging end hook formationslongitudinally flanking the first-mentioned pair, and formed astransversely pushed-out regions of the strap ends permitting limitedmovement of the strap ends in one longitudinal direction. These end hookformation are free of the lock formations. Thus these end hookformations can bear substantially all the load from the tension in thestrap, while the centaur hook formations with the lock formationsprevent them from unhooking. In practice it is standard to cut the strapto open the package, that is the connection at the ends is permanent andnot releasable.

[0011] The lock formations are formed as interfitting pyramidal orconical dimples. For best coupling, they pierce completely through oneof the strap ends. When th overlying strap is actually broken through bythe lock formation, the lock formations are particularly effective inpreventing relative slippage and uncoupling.

[0012] Each hook formation in accordance with the invention has an endportion defined between a pair of closely spaced and longitudinallyextending cuts, another end portion spaced longitudinally from the oneend portion and defined between a pair of widely spaced andlongitudinally extending cuts, and an intermediate portion between theend portions and formed between a pair of angled cuts each connecting arespective one of the closely spaced cuts with a respective one of thewidely spaced cuts. Titus these hook formations are generally T-shaped.

[0013] The lock formations are formed between the widely spaced cuts ofthe hook formations. In practice, the lock formations projecttransversely by a distance equal at least to a thickness of the strapends, normally twice this thickness.

[0014] The method according to the invention of joining a pair oflongitudinally extending and transversely overlapping strap endscomprises the steps of pushing regions out of the overlapping strip endsto form a pair of longitudinally extending and interengaging hookformations permitting limited movement of the strait ends in onelongitudinal direction. Then the pair of hook formations is deformed toform transversely interengaging lock formations fitting transverselysnugly together and prohibiting relative longitudinal movement of thestrap ends. As mentioned above, in accordance with the invention twofurther pairs of end hook formations are provided longitudinallyflanking the first-mentioned pair of hook formations. Normally they areproduced one after the other, first the one end hook formations with nolock formations, then the middle hook formation with the lockformations, and finally the other end hook formation with no lockformations.

[0015] The tool or apparatus for joining a pair of longitudinallyextending and transversely overlapping strap ends has according to theinvention an interengaging die and punch tools having wavy faces forpushing regions out of the overlapping strip ends forming the pair oflongitudinally extending and interengaging hook formations and a pin setin one of the tools for forming in the pair of hook formations thetransversely interengaging lock formations. The pin has a widthgenerally equal to a width of a cavity of the die tool and an end formedwith a tapered end with a flat end face. The pin is set in the punchtool and the cavity is formed with a recess in which the pin can fitloosely when the die tool and punch tool are fitted together. The pin isof hardened steel.

[0016] An advantage of this tool is that it is possible to adapt astandard strapping machine to produce the formations according to theinvention. All that needs be done is replace the die/punch assembly ofthe strapping machine. Since these elements are standard replaceableparts, upgrading to the system of this invention is particularly easy.

BRIEF DESCRIPTION OF THE DRAWING

[0017] The above and other objects, features, and advantages will becomemore readily apparent from the following description, reference beingmade to the accompanying drawing in which:

[0018]FIG. 1 is a side view of the end connection in accordance with theinvention;

[0019]FIG. 2 is a top view of the connection of FIG. 1;

[0020]FIG. 3 is a small-scale end view showing a package being strappedwith a tool according to the method of this invention;

[0021]FIGS. 4 and 5 are detail views of a part of the tool according tothe invention as it forms the connection according to the invention;

[0022]FIGS. 6 and 7 are side and top views of the die of the tool inaccordance with the invention; and

[0023]FIGS. 8 and 9 are top and side views of the die of the toolaccording to the invention.

SPECIFIC DESCRIPTION

[0024] As seen in FIGS. 1 and 2, two overlapping steel-strap ends 1 an 2are secured together at three hook formations 3 that are punched out ofthem. Each hook formation 3 is formed by a pair of transverselyrelatively closely spaced and longitudinally extending cuts 5, a pair ofmore widely spaced and also longitudinally extending cuts 6, and angledconnector zones 7 each extending from the end of one of the cuts 4 tothe end of the adjacent cut 5, leaving the ends 1 and 2 uncut atconnecting webs 15 between the hook formations 3. The ends 1 and 2 areformed with a series of corrugations or bumps corresponding to the hookformations 3 so that the hook formations 3 lock the ends 1 and 2together. The strap ends 1 and 2 are in fact as shown in FIG. 1 bentdownward to both sides of each of the hook formations 3 while the hookformations 3 are bent upward so that the hook formations 3 interengagein such a manner that, if these hook formations 3 were the only onesprovided on the ends 1 and 2, the two ends 1 and 2 could move limitedlylongitudinally apart before locking solidly together.

[0025] According to the invention the ends 1 and 2 are further formedwith interfitting dimple lock formations 4 located between the wideedges 6 of the center hook formations 3. These dimples 4 are of a heightequal to about twice the thickness of the strapping. They are so deepthat they in fact break through the sheet metal of the overlying strap,here the end 1. Thus they will solidly prevent the two interlocked ends1 and 2 from shifting longitudinally relative to ach oth r in eitherdirection.

[0026] As shown in FIGS. 3 through 9, a package 9, here a bale, issecured by means of a tool 8 having a die 10 and punch 11 that togetherform the hook formations 3 and dimples 4. Both the die 10 and the punch11 have wavy or corrugated faces and the die 10 is not pushed completelyinto the die to leave the connecting webs 15 in the ends 1 and 2 betweenthe hook formations 3. The punch 11 has as shown in FIG. 7 outer edges12 that fit complementary with inner edges 14 of a cavity 13 of the die10. In addition the punch 11 is formed with a rounded-end conical bump15 that can fit in a cylindrical recess 16 of the die 10.

[0027] In use as shown in FIGS. 4 and 5 the two die 10 and punch 11 arerocked together to first form the one pair of end hook formations 3,then the middle pair of hook formations 3 with the dimples 4, then theother pair of end hook formations 3. At the end of its rocking maneuver,after forming the third pair of end hook formations 3, the tool 8normally cuts through the strapping to form the outer end 1. In additionthe tool 8 normally also pulls the two ends 1 and 2 together beforemaking the hook formations 3 and 4.

We claim:
 1. A strapping connection for a pair of longitudinallyextending and transversely overlapping strap ends, the connectioncomprising: a pair of longitudinally extending and interengaging hookformations formed as transversely pushed-out regions of the strap endsand permitting limited movement of the strap ends in one longitudinaldirection; and transversely interengaging lock formations fittingtransversely snugly together, prohibiting relative longitudinal movementof the strap ends, and formed in the pair of hook formations.
 2. Thestrapping connection defined in claim 1, further comprising a secondpair of longitudinally extending and interengaging end hook formationsspaced longitudinally from the first-mentioned pair, formed astransversely pushed-out regions of the strap ends, permitting limitedmovement of the strap ends in one longitudinal direction, and free ofthe lock formations.
 3. The strapping connection defined in claim 1wherein the lock formations are formed as interfitting dimples.
 4. Thestrapping connection defined in claim 3 wherein the dimples arepyramidal.
 5. The strapping connection defined in claim 3 wherein thedimples are conical.
 6. The strapping connection defined in claim 1wherein the lock formations pierce completely through one of the strapends.
 7. The strapping connection defined in claim 1 wherein each hookformation has an end portion defined between a pair of closely spacedand longitudinally extending cuts, another end portion spacedlongitudinally from the one end portion and defined between a pair ofwidely spaced and longitudinally extending cuts, and an intermediateportion between the end portions and formed between a pair of angledcuts each connecting a respective one of the closely spaced cuts with arespective one of the widely spaced cuts.
 8. The strapping connectiondefined in claim 7 wherein the lock formations are formed between thewidely spaced cuts.
 9. The strapping connection defined in claim 1wherein the lock formations project transversely by a distance equal atleast to a thickness of the strap ends.
 10. A method of joining a pairof longitudinally extending and transversely overlapping strap ends, themethod comprising the steps of: pushing regions out of the overlappingstrip ends to form a pair of longitudinally extending and interengaginghook formations permitting limited movement of the strap ends in onelongitudinal direction; and a forming in the pair of hook formationstransversely interengaging lock formations fitting transversely snuglytogether and prohibiting relative longitudinal movement of the strapends.
 11. The method defined in claim 10, further comprising the step offorming two further pairs of end hook formations longitudinally flankingthe first-mentioned pair of hook formations.
 12. An apparatus forjoining a pair of longitudinally extending and transversely overlappingstrap ends, the apparatus comprising: means including an interengagingdie and punch tools having wavy faces for pushing regions out of theoverlapping strip ends a pair of longitudinally extending andinterengaging hook formations permitting limited movement of the strapends in one longitudinal direction and a pin set in one of the tools forforming in the pair of hook formations transversely interengaging lockformations fitting transversely snugly together and prohibiting relativelongitudinal movement of the strap ends.
 13. The apparatus defined inclaim 12 wherein the pin has a width generally equal to a width of acavity of the die tool and an end formed with a tapered end.
 14. Thapparatus defined in claim 13 wherein the tapered end has a flat endface.
 15. The apparatus defined in claim 13 wherein the pin is set inthe punch tool and the cavity is formed with a recess in which the pincan fit loosely when the die tool and punch tool are fitted together.16. The apparatus defined in claim 13 wherein the pin is of hardenedsteel.